JPH04303385A - Overload preventing device - Google Patents

Abstract

PURPOSE:To provide an overload preventing device having an adjusting device which can safely and easily carry out adjustment of a set load on the ground in a crane having the overload preventing device is installed on a swivel at the top of an extendible mast. CONSTITUTION:A crane has such a structure that the length of a mast 3 is increased by adding sub-masts 3a in accordance with the height of a building. An overload preventing device 11 is set on a swivel 4 which is positioned at the top of the mast 3. A wind-up rope 9 is suspended from a jib 5 attached to the swivel 4 so as to carry out a material handling work between the building on the ground and the latter. There are provided on the ground a load indicator 16 and means 24, 26 of adjusting the zero point of a specific load, for the overload preventing device 11. The means 24, 36, the load indicator 16 and the overload preventing device 11 are connected to each other by a remote control cable 18.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention has a structure in which the length of the mast is increased by adding split masts according to the construction height of the structure, and a rotating body is located at the top of the mast. The rated load set on the overload prevention device for climbing cranes and jib cranes that are equipped with an overload prevention device and perform cargo handling operations between above-ground structures and the ground by suspending hoisting ropes from the jib attached to the revolving structure. This invention relates to a device for adjusting.

0002

2. Description of the Related Art FIG. 4 is a side view showing a conventional climbing crane for constructing steel towers, and FIG. 5 is a side view showing the crane in a self-sustaining state at the initial stage of construction work. The climbing crane first constructs the base part 1a of the steel tower 1, and then assembles the mast lifting device 2 including a hydraulic cylinder supported by the base part 1a. A revolving body 4 is located at the top, and the revolving body 4 includes:
A support frame 6 having a sheave block on which a jib 5 is attached to be able to rise and fall freely, a winch 8 for winding up and letting out the support rope 7, and a winch 10 for the hoisting rope 9 are installed. . Moreover, the rotating body 4
An overload prevention device will be installed above.

[0003] This climbing crane performs work by remote control from the ground. As the construction of the steel tower 1 progresses, the mast lifting device 2 performs the work of lifting the entire crane by one segmented mast 3a and inserting a new segmented mast 3a under the mast 3. By repeating the process, the height of the mast 3 is increased according to the height of the steel tower 1. Finally, the height H of the mast 3 reaches 150 m to 160 m.

In such a climbing crane, the rated load of the overload prevention device is set as shown in the rated load curve a shown by the solid line in FIG. This setting is
This is carried out when the mast 3 is in the self-supporting state shown in FIG.

[0005]

[Problems to be Solved by the Invention] In the above-mentioned conventional climbing crane, when the tower is assembled, the lifting height becomes extremely large, 150 m to 160 m, as described above, and the hanging load is reduced by the weight of the hoisting rope 9. It turns out. To explain this using the rated load curve a in Fig. 6, W1 is the load on the hoisting rope 9 when the height of the mast 3 is at its maximum. In this case, the load on the hoisting rope 9 is about 0.2 t, and the load that can be lifted is a value W2 obtained by subtracting the weight of the hoisting rope 9 from the load shown in the rated load curve a.

[0006] As described above, when the steel tower 1 is assembled, the weight of the hoisting rope 9 is applied to the crane as a load, so that the load that can be lifted is reduced. As a result, the heavy lifting arm 1b may not be able to be hung before the assembly is completed, and it is necessary to adjust the set load of the overload prevention device installed on the revolving body 4 by the load of the hoisting rope 9. Conventionally, this adjustment was carried out by a worker climbing on the revolving structure 4, but since it was located at a high place, there were problems in that it was a heavy burden on the worker and was dangerous.

In view of these problems, the present invention provides an adjustment work that allows the adjustment of the set load to be easily and safely carried out on the ground in a crane in which an overload prevention device is installed on a revolving body at the top of the attached mast. An object of the present invention is to provide an overload prevention device having a device.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention has a structure in which the length of the mast is increased by adding split masts according to the construction height of the structure, and the top of the mast has a pivotable structure. In a crane that performs cargo handling work between an above-ground structure and the ground by suspending a hoisting rope from a jib attached to the revolving body, the revolving body is equipped with an overload prevention device. It is characterized by comprising a load indicator of an overload prevention device and a zero point adjustment means for rated load, and a remote control cable connects the zero point adjustment means and load indicator to the overload prevention device. do.

[0009]

[Operation] Since the overload prevention device of the present invention has the above structure, the hoisting rope is lowered from the mast until the hook lands on the ground, and the load indicator on the ground at that time shows zero. By operating the point adjustment means, the zero point of the set load of the overload prevention device is changed, and the set load that can be hoisted is adjusted to the one excluding the amount of the hoisting rope.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an embodiment of an overload prevention device according to the present invention. In FIG. 1, reference numeral 11 denotes an overload prevention device, which obtains the rated load corresponding to the jib angle represented by the curve shown in FIG. The load detector compares the actual load detected by a load cell installed between the end of the hoisting rope 9 and the jib 5, and if the actual load exceeds the rated load, it indicates the direction in which the load will increase. These winches 8 and 1 are operated so that the operations of the winches 8 and 1 (operating the winch 8 in the direction in which the jib 5 falls and operating the winch 10 in the hoisting direction) are stopped.
This is to control the stop relay 14 of 0.

Reference numeral 15 denotes a ground unit provided on the ground to adjust the zero point of the rated load of the overload prevention device 11, and the ground unit 15 includes a zero point adjustment load indicator 16 and a display value thereof. Adjust the overload prevention device 11
and a calibration dial 17 for changing the zero point of the set load. A signal cable 18 is suspended along the mast 3 between the operating unit 15 and the overload prevention device 11. 19 converts a voltage signal into a current signal or vice versa in order to prevent a signal error from occurring due to a voltage drop due to the electrical resistance of the signal cable 18.
is a voltage-to-current converter that allows signals to be transmitted in the form of current.

FIG. 2 is a circuit diagram showing a specific example of the zero point adjustment device of the present invention, and in the figure, reference numeral 20 indicates a load signal passed through a low-pass filter 21 from the load detector 13 to a subsequent processing circuit. The operational amplifier 20 is equipped with a variable resistor 22 for internal zero point adjustment and a variable resistor 23 for span adjustment, and also amplifies the output of the operational amplifier 20, that is, the actual load signal. Calculations are made between the circuit displayed on the load display 16 on the ground via the cable 18 (the voltage-current converter 19 is not shown) and the variable resistor 24 with the calibration dial 17 for adjusting the zero point of the load on the ground. It has a circuit that connects the input section of the amplifier 20 via a cable 18.

When performing zero point adjustment using this device, the worker stands on the ground and watches the value displayed on the load indicator 16 while keeping the hook 25 at the lower end of the hoisting rope 9 in contact with the ground. Meanwhile, the variable resistor 24 is adjusted using the calibration dial 17 so that the displayed value becomes zero. This allows zero point adjustment on the ground. With this adjustment, the output signal of the operational amplifier 20 becomes one obtained by subtracting the weight of the hoisting rope 9 from the top of the jib 5 to the ground, and the load signal of the load itself is output. As a result, the load set as the rated load can be lifted regardless of the height of the mast to be added. To explain this using Figure 6, the zero level of the load on the rated load curve is 0.
0', the rated load curve becomes as shown by the dotted line b, and the same load can be lifted as when the weight of the hoisting rope 9 is zero.

FIG. 3 shows another example of a circuit configuration for zero point adjustment. 30 is installed, and the variable resistor 24 can be adjusted by a knob 34 attached to the upper device 30, and is configured to be adjusted via a DC motor 32 and a speed reducer 33 that are remotely controlled from the ground. The DC motor 32 is energized and operated via a DC power supply 35 installed on the ground, an operation switch 36 having a polarity switching function, and a cable 18, and when the operation switch 36 is operated to either polarity side. The variable resistor 24 is operated while the load indicator 16 is being loaded, and the operator operates the operation switch 36 while looking at the value displayed on the load display 16.
Zero point adjustment becomes possible.

The present invention can be applied not only to cranes that raise the height of the mast, but also to cranes that construct masts by connecting them from above using a crane.

[0016]

According to the present invention, a load indicator of the overload prevention device and a zero point adjustment means for the rated load are provided on the ground side, and a gap between the adjustment means and the load indicator and the overload prevention device is provided. Since it is connected via a remote control cable, the operator can zero-adjust the rated load without having to climb the mast, which greatly facilitates adjustment, reduces the time required to climb the mast, and improves work efficiency. , improving work safety.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an overload prevention device according to the present invention.

FIG. 2 is a circuit diagram showing a specific example of a circuit for adjusting the zero point of the rated load in the embodiment.

FIG. 3 is a circuit diagram showing another example of the circuit of the present invention.

FIG. 4 is a side view showing an example of a crane to which the present invention is applied.

5 is a side view showing a state of the crane of FIG. 4 at an initial stage of assembly; FIG.

FIG. 6 is a rated load curve diagram of a crane that is a target of the present invention.

[Explanation of symbols]

1 Steel tower 2 Mast lifting device 3 Mast 3a Split mast 4 Swivel body 5 Jib 7 Jib support rope 8, 10 Winch 9 Hoisting rope 11 Overload prevention device 12 Jib angle detector 13 Load detector 14 Stop relay 15 Ground unit 16 Load indicator 17 Calibration dial 18 Cable 19 Voltage current converter 20 Operational amplifier 21 Filter 22 Variable resistance for internal zero point adjustment 23 Variable resistance for span adjustment 24 Variable resistance for zero point adjustment 32 DC motor 33 Reducer 34 Knob 35 DC power supply 36 Operation switch

Claims (1)

[Claims] Claim 1: The mast has a structure in which the length of the mast is increased by adding split masts according to the construction height of the structure, a rotating body is located at the top of the mast, and the rotating body is equipped with an overload prevention device. In a crane that performs cargo handling work between an above-ground structure and the ground by suspending a hoisting rope from a jib attached to the revolving structure, a load indicator of the overload prevention device and a zero point adjustment of the rated load are provided on the ground side. 1. An overload prevention device comprising: a remote control cable that connects the zero point adjustment means and load indicator to the overload prevention device.